Frequency multiplier



J. A. RAJCHMAN FREQUENCY M Aug. 6, 1946.

ULTIPLIER Filed April 30, 1942 Gttorneg Patented Aug. 6, 1946 STA E FREQUENCY MYULTIPLIER Jan A. Rajchman, Philadelphia, Pa., assignor to Radio Corporation of America, a corporation of Delaware 2 Claims. 1

This invention .relates generally to frequency multiplier-s and particularly to apparatus in which frequency multiplication is obtained by control of an electron beam in a cathode ray tube Whereby the frequency of a voltage impressed upon the deflecting elements of such a tube may be'multiplied to any other desired frequency, harmonic or otherwise.

The invention i an improvement on the system described in 'U. S. Patent 2,086,994 granted to John Evan on July 13, 1937, in that the instant invention is adapted more efficiently to derive extremely high output frequencies. The invention has particular utility in the generation of ultra high frequencies where an economical system of satisfactory frequency stabilization is desired. It permits the use of a crystal controlled oscillator, or other generator, of a fundamental frequency which can be accurately regulated, and the development of oscillations of any desired multiple of the fundamental frequency. The desired factor of frequency multiplication is obtained by suitable design of one of the electrodes of a cathode ray tube. Likewise, the wave form of the multiplied frequency may be controlled by the design of the multiplying electrode.

The use of a cathode ray tube for frequency multiplication is highly desirable since thg electron beam i substantially devoid of inertia and therefore enables the generation of extremely high output frequencies. Energy may be applied to the deflection elements of a cathode ray tube to produce a beam trace of any desired form and having any desired speed of rotation.

Among the objects of the invention are to provide an improved frequency multiplier of the cathode ray type in which any desired factor of multiplication may be obtained. Another object of the invention is to provide an improved frequency multiplier in which currents of considerable amplitude may be generated at ultra high frequency. Still another object of the invention is to provide improved means for stabilizing ultra high frequency currents.

The invention will be more clearly understood upon reference to the drawing in which Fig. l is a schematic diagram of a preferred embodiment of the invention, Figs. 2 and 3 are schematic diagrams of modifications of the invention, and Figs. 4 and 5 are plan views of apertures of different shapes which may be employed in the invention.

Referring to Fig. l, a cathode ray tube having an envelope i includes an electron emissive cathode 5 and a heater 2 which is supplied with power from the battery or other source 3, through a variable resistor t. Electrons emitted from the cathode 5 are accelerated and focused by the anode 6, which is connected to a point on the voltage divider 93, connected across the source of high potential M. A grid-aperture electrode l I, connected to a source of negative potential is disposed between the cathode and anode to confine the electron beam to useful proportions. Horizontal and vertical deflection elements and 8 are connected to a source of phase quadrature currents which are derived from a source of oscillation-s H! of the fundamental frequency to be multiplied. An accelerating electrode l2, which is optional, is connected to a second positive point on the voltage divider iii. A disc shaped electrode l5, having a plurality of apertures 25 of predetermined size, shape and relative spacing, is placed in the path of the deflected electron beam in such a manner that the apertures interrupt the beam a predetermined number of times during each rotation of the beam by the deflecting voltages.

In order to converge the path of the interrupted rotating beam to a small cross sectional area,

the electrostatic focusing elements it, I1, and it, which are connected respectively to proper points on the voltage divider l3, are disposed in axial relation with the electrode l5. The con stantly interrupted beam is thereby focused through an aperture 22 of a cavity resonator electrode it) to the small target electrode 2i.

Suitable coupling means 233 are provided for deriving energy for the load circuit 23 from the resonant electrode i9, which may be in the form of a cavity resonator of the type well known in ultra high frequency generators. The cavity resonator l9 and the target electrode 2| are connected to suitable biasing potentials from the voltage divider G2.

The invention has a distinct advantage over previously known devices in that the cavity res,- onator and target electrodes have extremely low capacitive coupling with respect to the other electrodes in the tube, thereby providing eflicient operation at extremely high frequencies. The particular arrangement has the additional advantage that the A. C. component of the output frequency may be derived from the coupling circuit 28, associated with the cavity resonator i9, and the D. C. component may be confined to the circuit including the target electrode 2|. If desired, a

load 23' may be connected simultaneously with said load 23, for example, by opening the switch I) 24, in the circuit connecting the voltage divider l 3 and the target electrode 2 l With the apparatus just described it is perfectly practicable to apply a stabilized frequency of, for example, 100 megacycles to the beam deflection elements I and 8. By providing 100 apertures in the electrode l5, it is possible to derive an output of 10,000 megacycles from the coupling circuit 20. If the frequency multiplication is of a low value, the resonant electrode may be omitted, and the output frequency derived directly from the target electrode 2|.

Fig. 2 is a modification of the system described by reference to Fig. 1 in that a magnetic focusing element 26 is substituted for the electrostatic focusing elements I6, I! and IS. A suitable source of power 21 is connected to the winding of the element 26.

Fig. 3 is a further modification of the system of Fig. 1 in that horizontal and vertical deflection elements 36 and 31 are substituted for the electrostatic focusing elements Hi, I! and I8, and so connected to the source of oscillations lB that the original deflection of the beam is effectively neutralized, and the interrupted beam made to converge to the small cross-sectional area required for the small target electrode 2 l.

Figs. 4 and 5 are illustrative of the versatility of the invention in that various shapes and spacing of the apertures 25in the electrode l5, may be combined with predetermined electron beam cross-sectional dimensions E, E", which may be derived in any well known manner, to

provide desired wave shape for the output frequency. Heretofore, the control of the wave shape of currents of ultra-high frequency has fre quently involved a serious loss in efliciency. This disadvantage is substantially reduced with the system described. Of course, if the output frequency is extremely high, considerable difliculty may be encountered in coupling efliciently to the cavity resonator l9 insofar as harmonic components of the output frequency are concerned.

I claim as my invention:

1. A signal frequency multiplier including a cathode ray device having means for generating an electron beam, an electrod having a lurality of apertures in thepath of said beam, beam deflecting means responsive to said signal for scanning said apertures, a relatively small target electrode, a cavity resonator disposed between said apertured electrode and said target electrode, means for converging and directing said beam from said apertured electrode through said cavity resonator to said target electrode, means for deriving energy from said cavity resonator in the form of alternating currents, and additional means for simultaneously deriving energy from said target electrode in the form of pulsating direct currents.

2. Apparatus as claimed in claim 1 wherein said apertures in said apertured electrode are substantially square in shape and wherein said beam is directed diagonally across each of said apertures.

JAN A. RAJ CHMAN. 

